Final answer:
The condition where a patient tries to brush their teeth with a pen is called ideomotor apraxia, which involves a disruption in coordinating motor commands for task-specific actions.
Step-by-step explanation:
When a patient attempts to brush their teeth but picks up a pen instead, this is an example of ideomotor apraxia. This condition involves a disruption in the ability to make the proper movements needed to complete a task, despite understanding the action and having the physical ability to perform it. Ideomotor apraxia is characterized by difficulties in coordinating motor commands with the appropriate tool or action, causing the patient to use the wrong object for a familiar task, such as using a pen to brush teeth.